Development of criteria to evaluate uniaxial creep data and asphalt concrete permanent deformation potential
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abstract
The uniaxial creep test is effective in identifying the sensitivity of asphalt concrete mixtures to permanent deformation or rutting. The creep test should be performed at a realistic testing temperature and at a stress level approximating field stress conditions. The creep test is shown to be sensitive to mixture variables including asphalt grade, binder content, aggregate type, air void content, temperature of testing, and testing stress state. Three parameters from the creep test are identified as effective indicators of mixture permanent deformation sensitivity: total strain at 1 hr of loading, p; the slope of the steady state portion of the plot of total strain versus time of loading, m; and the creep stiffness, Sc. In addition to the creep test parameters p and m, the sum of the total resilient strain from the dynamic compressive modulus test, ASTM D 3495, and p should be less than one-half of the strain at failure recorded in the unconfined compression test performed in accordance with the instructions in NCHRP Report 338, which explains the Asphalt Aggregate Mixture Analysis System.
